Piston



June 2, 1925.

E. O. BARSTOW ET AL PISTON Filed A1192. 10, 1921 Patented June 2, 1925.

UNITED STATES PATENT OFFICE.

EDWIN O'. BARSTOW AND NORMAN A. BEST, OF MII LAND, MICHIGAN, ASSIGNORS TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF 7 MICHIGAN.

PISTON.

Application filed August 10, 1921. Serial No. 451,135.

To all whom it may concern: I

Be it known that we, EDWIN O. BARSTOVV and NORMAN A. Beer, citizens of the United States, and residents of Midland, county of Midland, State of Michigan, have jointly invented a new and useful Improvement in Pistons, of which the following is a specification, the principle of the invention being herein explained and the best mode in which we have contemplated applying that principle, so as to distinguish it from other inventions.

Various attempts have been made to overcome the undue expansion of internal combustion engine pistons formed of light metal alloys or rather to compensate for the effects of such expansion by so constructing the piston, particularly the sleeve or skirt portion thereof, so that it is atomatically circumferentially compressible under the pressure exerted by the cylinder walls upon said sleeve or skirt when the piston expands. The use of so-called slit skirt pistons indeed has been found advantageous in connection with ordinary cast iron pistons, but usually in such case means have been provided for positively expanding the sleeve or skirt in order to render the diameter of the latter adjustable and thus take up wear.

The object of the present invention is the production of a light metal alloy piston, primarily one designed for use in in ternal combustion engines, in which piston the expansion of the sleeve or skirt-will be restrained or limited so as to correspond with or at least not exceed that of the cylinder walls which are ordinarily made of cast iron To the accomplishment of the foregoing and related ends the invention then consists of the means hereinafter fully described and particularly pointed outin the claims, the annexed drawing and the following description setting forth in detail certain means for carrying out the invention, such disclosed means illustrating, however, but several of the various waysin'which the principle of the invention may be used.

In said annexed drawing Fig. l is'a central vertical section of a piston embodying our present improve ments; Fig.2 is a bottom plan view of the same; Fig. 3 is a vertical section of a detail, the plane of the section being indicated by also showing a portion of the engine cylinder in which such piston is mounted; and Fig. 6 is a transverse section of such modified construction of piston, the plane of the section being indicated by the line 66 Fig. '5. r

In its general features of construction our present improved piston is similar to those of cast iron or light metal alloy heretofore used in internal combustion engines. In other words, such piston comprises a cylindrical head portion 1 from which de ends a sleeve or skirt portion 2, the latter eing open at its lower end. Such sleeve or skirt portion is formed with oppositely placed inwardly directed bosses 8, a ertured to receive the wrist in 4 (shown in Fig. 5 only) whereby the piston is attached to the connecting rod.

The skirt portion of the piston is desirably made of slightly larger diameter externally than the upper portion of the side wall surrounding the head proper, inasmuch as the latter is exposed to a higher temperature and consequently is subject to greater expansion. In order efl'ectually to seal such piston head within the walls of the cylinder 5 (see Fig. 5) in which it works, resilient piston rings (not shown) are seated in annular recesses 6 in the head portion, as need not be further explained.

Referring particularly to the form of our invention illustrated in Figs. 1 to 4 inclusive, it will be seen that the skirt portion 2 is slit with a number of cuts 10 extending in a general longitudinal direction although the form and disposition of such slits may be varied. (last on the inner faces of the resulting segments of such skirt portion are lugs 11 transversely recessed to receive and hold a cast iron ring 12. There is preferably one such lug 11 for each segment, the lug being disposed midway between the respective edges of the segment, and such lug is furthermore formed as shown in 4 Figs. 3 and 4 so as to hold the ring 12 in spaced relation from the segments of the skirt 2. In other words, the ring contacts with the skirt only at these lugs. Furthermore said ring is preferably split at -one point in its circumference and pro vided With means for ad usting its diameter,

- effect of which would be to contract the diameter of the piston skirt except as such contractionis opposed and limited by such ring 12. It will be understood that the piston is turned or ground to size after the ring 12 is in place and accordingly since the skirt can at no time have an expansion in excess of that of the cast iron ring (in fact, it will be somewhat less since the inward resilient pressure of the skirt segments offsets correspondingly the outward expansive force of the ring 12) the piston will never tend to' bind in the cylinder 5.

If desired to substantially entirely eliminate expansion of the-piston skirt, this can be accomplished by making the ring 12 of a nickel steel or other alloy having a very low coeflicient of expansion. Thus, for example, with the 'ring 12 made of the ironnickel alloy known under the trade name of invar and the skirt arranged-and constructed as above described, such skirt will remain of substantially uniform diameter throughout the entire range of working temperatures to which the piston is subjected in an internal combustion engine.

It willbe obvious that instead of having a ring 12 within theskirt portion of the piston so as to oppose the inward pressure of the segments of such skirt, the same result can be secured. by placing a ring on the outside of the skirt so as to restrain the outward expansion of the segments. Thus as shown in Figs. 5 and 6, we may form the skirt with an encircling groove or depression 15 adapted toreceive a continuous ring 16, the latter being. of such diameter relatively to that of the groove-bottom in the original condition of the piston (1. e. before ring is applied) that the segments of the skirt. will remain under tension under all conditions of use; that is they will expand to the full extent that the expansion of the ring will permit as the piston becomes heated up, while at the same time such ring as it cools will force the segments together so as correspondingly to reduce the diameter of the skirt. g

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as our invention 1. A piston comprising a head and a longitudinally slit skirt portion, and means controlling the inherent tendency of the latter to expand radially under an increase in temperature, said means comprising an annular member having a diflerent coeflicie'nt of expansion inserted within said skirt portion so as to retain same in a condition of inwardly directed tension at all working temperatures, said member contacting with said skirt portion at circumferentially spaced points only.

2. A' piston comprising a head and a skirt portion, the latter being formed of a light metal alloy, and means controlling the inherent tendency of such skirt portion to expand radially under an increase in temperature, said means comprising a member formed of a metal having a relatively lower coefficient of expansion than said skirt portion insertedwithin the latter so' as to retain same in a condition of inwardly directed tension at all working temperatures, said member contacting with said skirt portion at circumferentially spaced oints only.

3. A piston comprising a ead and a skirt portion, the latter being longitudinally slit and formed of a light metal alloy, and

means controlling the inherent tendency of such skirt portion to expand radially under an increase in temperature, said means com'- prising a member'formed of a metal having a relatively lower coetficient of expansion than said skirt portion inserted within the latter so as to retain same in a condition of inwardly directed tension at working tem peratures.

4. In an internal combustion engine, the combination with a cylinder of cast iron, a piston! reciprocable therein comprising a head and a skirt portion, the latter being longitudinally slit and formedof a light metal alloy, transversely recessed lugs on the inner faces of the segments of the skirt portion between said slits, and an annular member of adjustable-diameter formed of a metal having approximately the same coefiicient of expansion as said cylinder seated in the recesses of said lugs and adjusted to an initial degree of pressure against said lugs, the segments of said skirt portion beingformed to give an inward resilient pressure against said annular member at all working temperatures.

Signed at Midland, Michigan, this 5th day of August, 1921.

EDWIN o. BARSTOW, NORMAN A. BEST.

CERTIFICATE or cehREcTwN,

Patent No. 1,540,306. I I Granted .iune 2, 1928. to EDWIN o. cansrow ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 103, claim 3,

before the word Working" insert the word "all", and line 104, after the syllable "peratures" and before the period insert'a comma and the irords said member contacting with said skirt portion at circumferentially spaced points only"; and

that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the PatentOifice.

Signed and sealed this 23rd day of April, A. D 1929.

M. L Moore, i Seal) Acting Commissioner of Patents.. 

